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Not Applicable
1. Field of the Invention
The present invention generally relates to tachometers and, more particularly, to tachometers for engines of motor vehicles having transmissions with a plurality of gears.
2. Background of the Invention
Typically, engine speed is indicated by shaft rotation in revolutions-per-minute (rpm). During operation of a motor vehicle it is common to measure current engine rpm with vehicle instruments and to display the current engine rpm to the operator with a tachometer. The motor vehicle operator can read the display and determine whether or not to shift gears and/or to adjust the speed of the motor vehicle. The operator should shift gears at appropriate engine speeds to extract maximum power from the engine and obtain maximum vehicle speed. Up-shifting, that is, shifting to a higher transmission gear, too early can result in a loss of torque and resulting loss of vehicle acceleration or even engine stalling. Up-shifting too late can result in over-revving the engine, that is, reaching an engine speed greater than the maximum recommended engine speed, can cause damage to the engine valve train. Down shifting, that is, shifting to a lower transmission gear, at an inappropriate time can result in over-revving the engine, xe2x80x9credliningxe2x80x9d the engine, an/or even xe2x80x9cblowingxe2x80x9d the engine.
Often a motor vehicle""s engine performance is measured in a laboratory on a dynamometer or dynamo which measures engine torque, speed and power characteristics. In this way, peak torque and peak power values can be determined so that the operator can memorize and use them as an aid to obtain optimum gear shifting. Also, many operators memorize the sound of the engine as an aid to obtain optimum gear shifting.
While motor vehicle operators may be able reasonably shift at appropriate times, it is impossible to precisely know the effect of every gear shift operation under all conditions. The situation is further complicated when engines have variable controls because the peak torque value and the peak power value can change. With variable controls, it is impossible for a driver to even know the peak torque value and the peak power value under all conditions. Accordingly, there is a need in the art for a tachometer which enables the operator to shift gears in a manner which obtains improved motor vehicle performance.
The present invention provides a tachometer which overcomes at least some of the above-noted problems of the related art. According to the present invention, a tachometer comprises, in combination, a display adapted to produce an observable indication of a current rpm value for a current gear and an observable indication of at least one predicted rpm value for a different gear. The tachometer preferably includes a controller operably connected to the display and adapted to provide signals representing the current rpm value for the current gear and the at least one predicted rpm value for the different gear. In a preferred embodiment, the controller is adapted to calculate the at least one predicted rpm value with stored equations.
According to another aspect of the present invention a motor vehicle comprises, in combination, a transmission having a current gear which is engaged and at least one different gear which is not currently engaged and a tachometer. The tachometer includes a display adapted to produce an observable indication of a current rpm value for the current gear and an observable indication of a predicted rpm value for the different gear. The tachometer preferably further includes a controller operably connected to the display and adapted to provide signals representing the current rpm value for the current gear and the predicted rpm value for the different gear. In a preferred embodiment, the controller is adapted to calculate the predicted rpm value with stored equations.
According to yet another aspect of the present invention a method of providing rpm information comprises the steps of, in combination, producing an observable indication of a current rpm value for a current gear with a display and producing an observable indication of at least one predicted rpm value for a different gear with the display. The method preferably further comprises the steps of providing a signal representing the current rpm value for the current gear with a controller operably connected to the display and providing a signal representing the at least one predicted rpm value for the different gear with the controller. A preferred method further comprises the step of calculating the at least one predicted rpm value with stored equations of the controller.
From the foregoing disclosure and the following more detailed description of various preferred embodiments it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology and art of motor vehicle tachometers. Particularly significant in this regard is the potential the invention affords for providing a high quality, reliable, user-friendly device which enables a motor vehicle to operate at or near peak performance. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.